Cemented tantalum carbide



Patented Sept. 1, 1936 UNITED STATES PATENT OFFICE General Electric Company,

New York a corporation of No Drawing. Application October 28, 1930,

SerialNo. 491,814 r n 7 10 Claims. (01. 75136) The present application is a continuation-inpar of my copending application,

ing or binder medium ticles in the composition.

Cemented carbide produced in accordance with the nary grinding wheels. It is a further object to provide a cemented carbide tool suitable for cutting steel. Other objects of the invention appear hereinafter.

In carrying out my invention, I employ tantalum carbide as the main constituent of the cemented carbide, the binder or cementing medium consisting of two metals, one an element of the sixth group of Mendelejeifs table of eleand the other a metal of the iron group. The tantalum carbide may be prepared by adding grams of carbon, for example gas coke, to 181.5 grams of tantalum, and talum and carbon together for about five hours. The milling produces a very intimate mixture of the materials which are then fired at a temperature varying from 1550 to 1600 C. for about 8 hours in a closed graphite tube and in a hydrogen furnace. A similar carburizing process is dis? closed in my copending application, Serial No. 308,565, filed September 26, 1928.

The carbide thus formed is golden brown in color and is milled to break it up into a fine powder capable of passing through a 250 mesh screen. It is then mixed with a suitable amount of a metal binder medium, for example with about 13% of a mixture of iron and molybdenum, the iron and molybdenum being present in the binder preferably in the ratio of about 63 parts by weight of iron to about 37 parts of molybdenum. The mixture of tantalum carbide and binder material is pressed into any desired shape in a hydraulic press.

The pressed material, usually in the form of a tool bit, is sintered in a closed graphite tube in a hydrogen furnace at a temperature of about 5 1400 C. for about 1 hours. If the cemented tantalum carbide bit thus formed is copper a flux, for example borax, in good joint. 10

Although the cemented tantalum carbide composition containing about 13% binder material has a relatively low modulus of rupture as compared with that of cemented tungsten carbide employing the same quantity of binder material, a tool bit of this composition gives very satisfactory results. as above described when tested on a nickel steel log with a cut of a feed of 55 mils for 10 minutes at feet per minute was perfectly sharp at the end of the test and showed no signs of wear at any point. The same tool without 35 being resharpened was again tested for 8 minutes chip to wear a slight depression just back of the cutting edge of the tools. I have found how- 45 at relatively high 50 such conditions is similar to that obtainedby 55 tantalum carbide and 13% 2 the use of a grinding wheel. It is my present opinion that the ability of cemented tantalum carbide to produce a smooth finish and to remove the material from the work without injury to the tool bit, is due to the fact that the cemented tantalum carbide apparently cuts the metal and does not drag it ofi.

As a binder material for tantalum carbide, I prefer to employ the eutectic composition consisting of about 63 parts iron and 37 parts molybdenum and having a melting point of about 1440" C. My invention howeveris not limited to this particular binder. Other binder or cementing mediums may be employed with tantalum carbide if desired, for example a binder consisting of an iron-molybdenum compound constituting of about 53 parts molybdenum with about 47 parts iron and having a melting point of about 1530 C., or a binder consisting of about 45 parts nickel and about 55 parts tungsten and having a melting point of 1460 C., or a binder consisting of about 66' parts nickel and about 34 parts tungsten and having a melting point of 1495 C. However, I have obtained the most satisfactory results with molybdenum-iron binders and particularly with the eutectic binder consisting of about 63% iron and about 37% molybdenum.

Although I have described my invention in connection with a composition consisting of 87% binder material, the invention is not limited to these particular percentages. I'he above quantities, while illustrative of my invention may be varied considerably depending upon the qualities desired in the finished material.

What I claim 'as new and desire to secure by Letters Patent of the United States, is:

1. A sintered, hard, metal composition consisting of tantalum carbide and a binder medium therefor, said binder medium comprising about .3 to about 20% I of said composition and consisting substantially of about 34% to about 55% of metal of the sixth group of Mendelejeff's table of elements of the periodic system and about 45% to about 66% of metal of the iron group.

2. A sintered, hard, metal composition consisting of tantalum carbide and a binder medium therefor, said binder medium comprising about 3 to about 20% of said composition and consisting substantially of about 34% tungsten and 66% nickel.

3. A sintered, hard, metal composition consisting of tantalum carbide and a binder medium therefor, said binder medium comprising about 3 to about 20% of said composition and consisting substantially of about 63 parts by weight of iron and 37 parts by weight of molybdenum.

4. A sintered, hard, met-a1 composition consisting of tantalum carbide and a binder medium therefor, said binder medium comprising about 3 to about 20% of said composition and consisting substantially of about 53 parts by weight of molybdenum and about 47 parts by weight of iron.

5. A hard, tough, cemented carbide composition containing from about 3 to about 20% of a binder material, the remainder of the composition being tantalum carbide, said binder containing about 45 parts by weight nickel and about 55 parts by weight of tungsten.

6. An alloy comprising substantially 9% by weight of molybdenum, substantially 11% by weight of nickel, and substantially by weight of tantalum carbide.

7. An alloy comprising substantially 9% by weight of tungsten, substantially 11% by weight of nickel, and substantially 80% by weight of tantalum carbide.

8. A sintered composition consisting substantially of tantalum carbide particles, metal of the iron group and metal of the sixth group of Mendelejefi's periodic table of elements, said tantalum carbide particles being bonded into a hard, tough mass by a cementing medium consisting substantally of said metal of the iron group and said metal of the sixth group.

9. An alloy consisting substantially of tantalum carbide, metal of the iron group and metal from a group consisting of tungsten and molybdenum, the tantalum carbide comprising at least 80% by weight of said alloy.

10. An alloy consisting substantially of tantalum carbide, nickel, and metal from a group consisting of tungsten and molbdenum, the tantalum carbide comprising at least 80% by weight of said alloy and the nickel being in excess of the metal from said group.

FLOYD C. KELLEY. 

